This invention relates generally to gas turbine engines, and more particularly to methods and apparatus for assembling gas turbine engines.
At least some known gas turbine engines include axisymmetric structures, such as combustors for example. During operation, thermal differentials between the concentric axisymmetric flowpath components may result in thermal stresses being induced. Although providing for relative radial movement between the concentric axisymmetric structures may facilitate reducing such thermal stresses, such arrangements make it more difficult to maintain at least some of the axisymmetric hardware substantially concentric to the engine centerline axis to facilitate proper operation of the gas turbine engine. Moreover, thermal differentials between the axisymmetric structures may result in excessive loads resulting in relatively high cyclic stress and/or fatigue cracks in the axisymmetric structures.
One known method of resolving the thermal differential problem is illustrated in FIG. 1. As shown in FIG. 1, at least one known gas turbine engine includes a combustor casing that includes a plurality of radially oriented pins 2 that engage female bushings 3 that are coupled to the combustor 4. The pins are threaded into the combustor outer casing 5, which surrounds the combustor. In operation, the combustor, which is considerably hotter than the casing, is free to expand in a radial direction.
However, as shown in FIG. 1, to assemble the combustor within the gas turbine engine, the dimensional tolerances of the components require a radial clearance in the fit of the male pin to the female bushing to permit assembly. As a result, during operation, only a portion of the radial pins support the axial load and react to tangential forces. As such, these radial pins may experience increased wear compared to other radial pins utilized to support the combustor. In addition, slight dimensional misalignment of either the pins, the bushing bores, or both, may cause the load to be concentrated on either the edge of the bushing and/or the end of the pin. This concentrated load on what is initially a point contact on the pin and/or bushing again may result in increased wear of the bushing and/or the pin.